The present disclosure relates to thermoplastic olefin compositions, specifically to a thermoplastic olefin compositions for vacuum forming.
Vacuum forming includes both positive molds (i.e., male) and/or negative impressions (i.e., female). A typical vacuum forming process includes employing a negative pressure (i.e., a vacuum), between a sheet of material to be molded and the mold itself. The sheet is typically heated to a controlled softening temperature and subsequently stretched to conform to the mold contours to impart a desired shape of the part. This process may also be assisted by a plug assist and/or one or more vacuum holes in the mold. Once formed, the molded material is then cooled and the excess material removed (e.g., trimmed) to yield a final part and/or assembly.
Material properties that affect vacuum forming include melt flow rate, depth of draw, resistance to thinning, coefficient of friction, grain retention, and the like. However, material properties required for negative or female vacuum forming, also known as mold grain forming applications, are typically different from or even in opposite to those required for male vacuum forming applications. For example, in male vacuum forming, a high grain retention after vacuum forming is preferred. In contrast, in female vacuum forming, a relatively high melt flow rate to allow for greater depth of draw and increased resistance to excessive thinning, along with a lower coefficient of friction on tool surfaces are preferred. Accordingly, materials suitable for male vacuum forming may not necessarily be suitable for female vacuum forming. Since male vacuum forming is practiced almost to the exclusion of female vacuum forming, it would be beneficial to have materials suitable for female vacuum forming. Of particular benefit would be a thermoplastic olefin compositions suitable for female vacuum forming, preferably both male and female vacuum forming.
Disclosed herein is a thermoplastic olefin composition, comprising, based on the total weight of the composition: about 20 wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt % ethylene copolymer; and less than or equal to about 30 wt % linear low density polyethylene.
Also disclosed herein is a process of forming a thermoplastic olefin composition comprising: combining, based on the total weight of the composition, about 20 wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt % ethylene copolymer; and less than or equal to about 30 wt % linear low density polyethylene, to produce the thermoplastic olefin composition.
Further disclosed herein is a thermoplastic olefin composition, comprising a reaction product of, based on the total weight of the composition: about 20 wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt % ethylene copolymer; and less than or equal to about 30 wt % linear low density polyethylene.
Additionally disclosed herein is a process for vacuum forming an article, comprising: mixing about 20 wt % to about 40 wt % polypropylene, about 30 wt % to about 70 wt % ethylene copolymer, and less than or equal to about 30 wt % linear low density polyethylene to form a blend, based upon a total weight of the blend; and forming a sheet from the blend; heating the sheet to a softening temperature; disposing the sheet in a mold; and vacuum forming the sheet into an article.
Also disclosed herein is an article of manufacture comprising, based on the total weight: about 20 wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt % ethylene copolymer; and less than or equal to about 30 wt % linear low density polyethylene.
In addition, disclosed herein is an automotive assembly comprising, based on the total weight of the assembly: about 20 wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt % ethylene copolymer; and less than or equal to about 30 wt % linear low density polyethylene.
The above described and other features are exemplified by the following detailed description.